Magnetic alloy



Patented Mar. 26, 1935 PATENT OFFICE MAGNETIC ALLOY Vere B. Browne, Brackenridge, Pa., assignor to Allegheny Steel Company, a corporation of Pennsylvania No Drawing. Application July 3, 1934, Serial No. 733,633

9 Claims.

This invention relates to magnetic alloys for use in the make-up of laminated structures for electrical apparatus such as transformers, dynamos, motors and the like, and since the predominating element of most materials used for this purpose is iron, these materials are not only known as magnetic alloys but as electrical steels as well.

Since magnetic alloys or electrical steels are 10 used principally for the building up of laminated structures, they are usually reduced to sheetlike form and embrace strip material as well as sheet material produced both by hot rolling operations entirely and by a combination of hot and cold rolling operations.

The magnetic alloys or electrical steels which are most commonly used for forming sheet-like material from which the cores of transformers, generators, motors and other electrical apparatus are built up, are those in which silicon or silicon and small percentages of aluminum are alloyed with iron.

In addition to aluminum, manganese up to .'7% has been suggested as an alloying element in connection with silicon for magnetic alloys or electrical steel.

As to the alloys of silicon and iron, the usual silicon range is from about 0.5% to about 5%, with the balance substantially all iron except for relatively small unavoidable amounts of such elements as phosphorus, sulphur and carbon. Where aluminum is used in addition to silicon, it is usually present in relatively small amounts.

The percentage of silicon contained in any of these alloys depends upon the use to be made of the particular alloy. Alloys containing about 0.5% silicon are used where the magnetic requirements, particularly as to energy or watt loss, are not severe, while alloys containing around 4% or more of silicon are used where the lowest energy losses are required, e. g., in transformers.

It is well known that alloys containing percentages of silicon in the lower part of this range possess fairly good ductility while those alloys which contain around 4% or more of silicon have much less ductility; so much less in fact that in some instances the alloys can be broken readily when stressed or subjected to relatively slight shock especially when cold. For this reason in particular, the iron silicon alloys which are used in the make-up of rotating parts of electrical apparatus such as the armatures of motors and generators have a lower silicon content than those used for stationary electrical apparatus, such as transformers and consequently it is necessary to sacrifice a large part of the benefits to be derived from the use of alloys having the higher silicon contents where such alloys are employed in the make-up of the moving parts of electrical apparatus. As will be understood from the foregoing, while the mechanical properties of magnetic alloys having the lower silicon contents are satisfactory, they cannot meet the requirements as to magnetic properties. This dilemma has faced theart for a number of years and the problem occasioned by it has not hitherto been satisfactorily solved.

In general, my invention resides in the production of an improved alloy and in the production of sheet and strip material made from such improved alloy and which not only have the desired magnetic characteristics, but also have excellent mechanical properties as well.

I have discovered that alloys of manganese, aluminum and iron with normal percentages of impurities such as phosphorus sulphur and carbon, when converted into the form of sheet and strip material possess excellent mechanical properties and such magnetic characteristics as make them especially suitable for the make-up of laminated structures for moving parts of electrical apparatus. Such material also possesses such magnetic characteristics that it may be used in the make-up of laminated structures of stationary electrical apparatus.

An example of an alloy embodying my present invention is one composed of approximately 3% manganese and approximately 3% aluminum with the balance substantially all iron except for the usual small amounts of impurities such as phosphorus, sulphur and carbon. When converted into strips or sheets having a thickness of .014 inches (29 gauge) and suitably annealed, such material will have a watt loss value less than about .700 watts per pound at 10,000 B. and cycles. For material of heavier gauge the watt loss will of course be greater and conversely for material of lighter gauge it will be less. In general the watt loss of 29 gauge material at 10,000 B. and 60 cycles may range up to about .700 watts per pound, more or less.

I have discovered that the percentage of manganese may range from approximately 1% to approximately 8% and that the amount of alu- 50 minum may range from approximately 1% to approximately 4%, the balance in all cases being substantially all iron except for the usual small amounts of impurities as above noted.

Sheet and. strip material made from such alloys have mechanical properties and magnetic characteristics which make them exceedingly useful for the building up of laminated structures for rotating parts of electrical apparatus, since these properties, both mechanical and electrical, are superior to the corresponding properties of the silicon iron or the silicon, aluminum iron alloys in which the silicon content is limited to that now used for rotating parts of. electrical apparatus.

It is noteworthy that the watt loss value of not over .700 watts per pound at 10,000 B. and 60 cycles for sheet-like material having a thickness of .014 inch, is considerably lower than the value obtained from the 3 to 3 /2% silicon steels of the same gauge or thickness frequently used for building up the laminated structures for rotating parts of electrical apparatus. This value compares very favorably with some of the grades of electrical steel of higher silicon content such as used in stationary electrical apparatus.

A magnetic alloy composed of manganese, aluminum and iron with the mechanical properties and electrical characteristics of the order noted represents an entirely new entity in this art insofar as I am aware.

The particular method of making the present alloy and the particular rolling and annealing procedures used for converting the same to the form of sheet or strip, do not, per se, form any part of the present invention, such being rather reserved for another application.

What I claim as new and desire to secure by Letters Patent is:

1. Magnetic sheet-like material for use in electrical apparatus and made from an alloy'containing about 3% manganese, and about 3% aluminum, the balance being iron except for the usual impurities which are present in common amounts and characterized by relativelylow watt loss values and good mechanical properties.

2. Magnetic sheet-like material foruse in electrical apparatus and made from an alloy containing from about 1-8% manganese, and from about l-4% aluminum, the balance being principally iron and characterized by low watt loss and good mechanical properties.

3. Magnetic sheet-like material for use in electrical apparatus and containing approximately 3% manganese, approximately 3% aluminum with the balance principally iron and characterized by a watt loss value of not over about .700 watts per pound at 10,000 B. and 60 cycles for material having a thickness of .014 inch, said watt loss value decreasing as the thickness of the material decreases.

4. Magnetic sheet-like material for use in electrical apparatus and made from an alloy containing from about 1-8% manganese, from about l-4% aluminum, with the balance substantially all iron and being characterized by a watt loss value of less than about .700 watts per pound at 10,000 B. and 60 cycles for 29 gauge material, said watt loss value decreasing as the thickness of the material decreases and increasing as the thickness of the material increases.

5. 'A magnetic manganese-aluminum-iron alloy containing about 3% manganese and about 3% aluminum, the balance being substantially all iron except for the usual amounts of carbon, phosphorus and sulphur, and characterized by a low watt loss and good mechanical properties when converted into sheet-like material of suitable gauge.

6. A magnetic manganese-aluminum-iron alloy containing about 1-8% manganese, about 1-4% aluminum, the balance being substantially all iron except for the usual amounts of carbon, phosphorus and sulphur and characterized by a relatively low watt loss and-good mechanical properties, when converted into sheet-like material of suitable gauge.

7. A magnetic manganese-aluminum-iron alloy containing about 3% manganese and about 3% aluminum, the balance being substantially all iron except for the usual amounts of carbon, phosphorus and sulphur and characterized by a watt loss per pound of less than about .700 at 10,000 B. and 60 cycles in 29 gauge material, said watt loss value decreasing as the thickness of the material decreases.

8. A magnetic manganese-aluminum-iron alloy containing about 1-8% manganese, about 1-4% aluminum, the balance being substantially all iron except for the usual amounts of carbon, phosphorus and sulphur and characterized by a watt loss per pound of less than about .700 at 10,000 E. and 60 cycles in 29 gauge material said watt loss value increasing as the thickness increases.

9. A magnetic manganese-aluminum-iron alloy containing approximately 1-8% manganese and 14% aluminum, the balance being substantially all iron except for the usual amounts of carbon,

phosphorus and sulphur and having a watt loss 1 value of less than about .700 Watts per pound at 10,000 B. and 60 cycles for. 29 gauge strip, said watt loss value decreasing as the thickness of the strip decreases.

' VERE B. BROWNE. 

